Here are some example parametric equations to plug in. The number of prims used can be reduced by lowering the steps_u and steps_v variables, though the surfaces will not look as good. It is also a good idea to lower the scale number as well, to avoid prims trying (and failing) to scale to above 10m along any dimension. The parametric equations are from: http://vmm.math.uci.edu/3D-XplorMath/Surface/gallery.html